Photocrosslinkable chitosan hydrogels and their biomedical applications

Advances in Chitosan-Based Smart Hydrogels for Colorectal Cancer Treatment

Despite advancements in early detection and treatment in developed countries, colorectal cancer (CRC) remains the third most common malignancy and the second-leading cause of cancer-related deaths worldwide. Conventional chemotherapy, a key option for CRC treatment, has several drawbacks, including poor selectivity and the development of multiple drug resistance, which often lead to severe side effects. In recent years, the use of polysaccharides as drug delivery systems (DDSs) to enhance drug efficacy has gained significant attention. Among these polysaccharides, chitosan (CS), a linear, mucoadhesive polymer, has shown promise in cancer treatment. This review summarizes current research on the potential applications of CS-based hydrogels as DDSs for CRC treatment, with a particular focus on smart hydrogels. These smart CS-based hydrogel systems are categorized into two main types: stimuli-responsive injectable hydrogels that undergo sol-gel transitions in situ, and single-, dual-, and multi-stimuli-responsive CS-based hydrogels capable of releasing drugs in response to various triggers. The review also discusses the structural characteristics of CS, the methods for preparing CS-based hydrogels, and recent scientific advances in smart CS-based hydrogels for CRC treatment.

The Impact of the Methacrylation Process on the Usefulness of Chitosan as a Biomaterial Component for 3D Printing

Chitosan is a very promising material for tissue model printing. It is also known that the introduction of chemical modifications to the structure of the material in the form of methacrylate groups makes it very attractive for application in the bioprinting of tissue models. The aim of this work is to study the characteristics of biomaterials containing chitosan (BCH) and its methacrylated equivalent (BCM) in order to identify differences in their usefulness in 3D bioprinting technology. It has been shown that the BCM material containing methacrylic chitosan is three times more viscous than its non-methacrylated BCH counterpart. Additionally, the BCM material is characterized by stability in a larger range of stresses, as well as better printability, resolution, and fiber stability. The BCM material has higher mechanical parameters, both mechanical strength and Young's modulus, than the BCH material. Both materials are ideal for bioprinting, but BCM has unique rheological properties and significant mechanical resistance. In addition, biological tests have shown that the addition of chitosan to biomaterials increases cell proliferation, particularly in 3D-printed models. Moreover, modification in the form of methacrylation encourages reduced toxicity of the biomaterial in 3D constructs. Our investigation demonstrates the suitability of a chitosan-enhanced biomaterial, specifically methacrylate-treated, for application in tissue engineering, and particularly for tissues requiring resistance to high stress, i.e., vascular or cartilage models.

Photopolymerization Approach to Advanced Polymer Composites: Integration of Surface-Modified Nanofillers for Enhanced Properties

The incorporation of functionalized nanofillers into polymers via photopolymerization approach has gained significant attention in recent years due to the unique properties of the resulting composite materials. Surface modification of nanofillers plays a crucial role in their compatibility and polymerization behavior within the polymer matrix during photopolymerization. This review focuses on the recent developments in surface modification of various nanofillers, enabling their integration into polymer systems through photopolymerization. The review discusses the key aspects of surface modification of nanofillers, including the selection of suitable surface modifiers, such as photoinitiators and polymerizable groups, as well as the optimization of modification conditions to achieve desired surface properties. The influence of surface modification on the interfacial interactions between nanofillers and the polymer matrix is also explored, as it directly impacts the final properties of the nanocomposites. Furthermore, the review highlights the applications of nanocomposites prepared by photopolymerization, such as sensors, gas separation membranes, purification systems, optical devices, and biomedical materials. By providing a comprehensive overview of the surface modification strategies and their impact on the photopolymerization process and the resulting nanocomposite properties, this review aims to inspire new research directions and innovative ideas in the development of high-performance polymer nanocomposites for diverse applications.

Extrusion-Based 3D Printing of Photocrosslinkable Chitosan Inks

Photocuring of chitosan has shown great promise in the extrusion-based 3D printing of scaffolds for advanced biomedical and tissue engineering applications. However, the poor mechanical stability of methacrylated chitosan photocuring ink restricts its applicability. The inclusion of co-networks by means of simultaneous polycomplex formation is an effective method by which to solve this drawback, but the formed hydrogel inks are not printable. This work aims to develop new photocurable chitosan inks based on the simultaneous photocrosslinking of methacrylated chitosan (CHIMe) with N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, and acrylic acid to be applied in extrusion 3D printing. Interestingly, the polycomplex co-network corresponding to the acrylic-acid-based ink could be successfully printed by the here-presented simultaneous photocuring strategy. Further, the conversion of photocrosslinking was studied via photo-DSC analyses that revealed a clear dependence on the chemical structure of the employed crosslinking agents (from 40 to ~100%). In addition, the mechanical and rheological properties of the photocured hydrogels were comparatively studied, as well as the printing quality of the extruded scaffolds. The newly developed chitosan photocurable inks demonstrated extrusion printability (squareness ~0.90; uniformity factor ~0.95) and tunable mechanical properties (Young modulus 14-1068 Pa) by means of different crosslinking approaches according to the chemical architecture of the reactive molecules employed. This work shows the great potential of photocrosslinkable chitosan inks.

Chitosan-based hydrogel wound dressing: From mechanism to applications, a review

As promising biomaterials, hydrogels are widely used in the medical engineering field, especially in wound repairing. Compared with traditional wound dressings, such as gauze and bandage, hydrogel could absorb and retain more water without dissolving or losing its three-dimensional structure, thus avoiding secondary injury and promoting wound healing. Chitosan and its derivatives have become hot research topics for hydrogel wound dressing production due to their unique molecular structure and diverse biological activities. In this review, the mechanism of wound healing was introduced systematically. The mechanism of action of chitosan in the first three stages of wound repair (hemostasis, antimicrobial properties and progranulation), the effect of chitosan deacetylation and the molecular weight on its performance are analyzed. Additionally, the recent progress in intelligent and drug-loaded chitosan-based hydrogels and the features and advantages of chitosan were discussed. Finally, the challenges and prospects for the future development of chitosan-based hydrogels were discussed.

Synthesis, Characterization, Properties, and Biomedical Application of Chitosan-Based Hydrogels

The prospective applications of chitosan-based hydrogels (CBHs), a category of biocompatible and biodegradable materials, in biomedical disciplines such as tissue engineering, wound healing, drug delivery, and biosensing have garnered great interest. The synthesis and characterization processes used to create CBHs play a significant role in determining their characteristics and effectiveness. The qualities of CBHs might be greatly influenced by tailoring the manufacturing method to get certain traits, including porosity, swelling, mechanical strength, and bioactivity. Additionally, characterization methods aid in gaining access to the microstructures and properties of CBHs. Herein, this review provides a comprehensive assessment of the state-of-the-art with a focus on the affiliation between particular properties and domains in biomedicine. Moreover, this review highlights the beneficial properties and wide application of stimuli-responsive CBHs. The main obstacles and prospects for the future of CBH development for biomedical applications are also covered in this review.

Enhancing Enzyme Activity and Thermostability of Bacillus amyloliquefaciens Chitosanase BaCsn46A Through Saturation Mutagenesis at Ser196

Chitosanase plays an important role in chitooligosaccharides (COS) production. We found that the chitosanase (BaCsn46A) of Bacillus amyloliquefacien was a good candidate for chitosan hydrolysis of COS. In order to further improve the enzyme properties of BaCsn46A, the S196 located near the active center was found to be a critical site impacts on enzyme properties by sequence alignment analysis. Herein, saturation mutation was carried out to study role of 196 site on BaCsn46A catalytic function. Compared with WT, the specific enzyme activity of S196A increased by 118.79%, and the thermostability of S196A was much higher than WT. In addition, we found that the enzyme activity of S196P was 2.41% of that of WT, indicating that the type of amino acid in 196 site could significant affect the catalytic activity and thermostability of BaCsn46A. After molecular docking analysis we found that the increase in hydrogen bonds and decrease in unfavorable bonds interacting with the substrate were the main reason for the change of enzyme properties which is valuable for future studies on Bacillus species chitosanase.

Photocrosslinkable natural polymers in tissue engineering

Natural polymers have been widely used in scaffolds for tissue engineering due to their superior biocompatibility, biodegradability, and low cytotoxicity compared to synthetic polymers. Despite these advantages, there remain drawbacks such as unsatisfying mechanical properties or low processability, which hinder natural tissue substitution. Several non-covalent or covalent crosslinking methods induced by chemicals, temperatures, pH, or light sources have been suggested to overcome these limitations. Among them, light-assisted crosslinking has been considered as a promising strategy for fabricating microstructures of scaffolds. This is due to the merits of non-invasiveness, relatively high crosslinking efficiency via light penetration, and easily controllable parameters, including light intensity or exposure time. This review focuses on photo-reactive moieties and their reaction mechanisms, which are widely exploited along with natural polymer and its tissue engineering applications.

Smart Bioinks for the Printing of Human Tissue Models

3D bioprinting has tremendous potential to revolutionize the field of regenerative medicine by automating the process of tissue engineering. A significant number of new and advanced bioprinting technologies have been developed in recent years, enabling the generation of increasingly accurate models of human tissues both in the healthy and diseased state. Accordingly, this technology has generated a demand for smart bioinks that can enable the rapid and efficient generation of human bioprinted tissues that accurately recapitulate the properties of the same tissue found in vivo. Here, we define smart bioinks as those that provide controlled release of factors in response to stimuli or combine multiple materials to yield novel properties for the bioprinting of human tissues. This perspective piece reviews the existing literature and examines the potential for the incorporation of micro and nanotechnologies into bioinks to enhance their properties. It also discusses avenues for future work in this cutting-edge field.

Photopolymerization of Bio-Based Polymers in a Biomedical Engineering Perspective

Photopolymerization is an effective method to covalently cross-link polymer chains that can be shaped into several biomedical products and devices. Additionally, polymerization reaction may induce a fluid-solid phase transformation under physiological conditions and is ideal for in vivo cross-linking of injectable polymers. The photoinitiator is a key ingredient able to absorb the energy at a specific light wavelength and create radicals that convert the liquid monomer solution into polymers. The combination of photopolymerizable polymers, containing appropriate photoinitiators, and effective curing based on dedicated light sources offers the possibility to implement photopolymerization technology in 3D bioprinting systems. Hence, cell-laden structures with high cell viability and proliferation, high accuracy in production, and good control of scaffold geometry can be biofabricated. In this review, we provide an overview of photopolymerization technology, focusing our efforts on natural polymers, the chemistry involved, and their combination with appropriate photoinitiators to be used within 3D bioprinting and manufacturing of biomedical devices. The reviewed articles showed the impact of different factors that influence the success of the photopolymerization process and the final properties of the cross-linked materials.

Chitosan-based smart hybrid materials: a physico-chemical perspective

Chitosan is one of the most studied cationic polysaccharides. Due to its unique characteristics of being water soluble, biocompatible, biodegradable, and non-toxic, this macromolecule is highly attractive for a broad range of applications. In addition, its complex behavior and the number of ways it interacts with different components in a system result in an astonishing variety of chitosan-based materials. Herein, we present recent advances in the field of chitosan-based materials from a physico-chemical perspective, with focus on aqueous mixtures with oppositely charged colloids, chitosan-based thin films, and nanocomposite systems. In this review, we focus our attention on the physico-chemical properties of chitosan-based materials, including solubility, mechanical resistance, barrier properties, and thermal behaviour, and provide a link to the chemical peculiarities of chitosan, such as its intrinsic low solubility, high rigidity, large charge separation, and strong tendency to form intra- and inter-molecular hydrogen bonds.

Tunable Thiol-Ene Photo-Cross-Linked Chitosan-Based Hydrogels for Biomedical Applications

Access to biocompatible hydrogels with tunable properties is of great interest in biomedical applications. Here we report the synthesis and characterization of a series of photo-cross-linked chitosan hydrogels from norbornene-functionalized chitosan (CS-nb) and various thiolated cross-linkers. The resulting materials were characterized by NMR, swelling ratio, rheology, SEM, and small angle neutron scattering (SANS) measurements. The hydrogels exhibited pH- and salt-dependent swelling, while the macro- and microscale properties could be modulated by the choice and degree of cross-linker or the polymer concentration. The materials could be molded in situ and loaded with small molecules that can be released overtime. Moreover, the incorporation of collagen in the hydrogels drastically improved cell adhesion, with excellent viabilities of human dermofibroblast cells on the hydrogels observed for up to 6 days, highlighting the potential use of these materials in the biomedical area.